This project is attempting the isolation and identification of lipid constituents responsible for the tissue changes in animal gingivae equatable with human periodontal disease. It is also attempting to elucidate the involvement of the lipids of this group of bacteria isolated from human periodontal lesions (some assayed for virulence in gnotobiotic animal models) with plaque formation, by testing the effects on cell to cell agglutination of both lipid active agents and of lipids isolated from specific cross agglutinating strains. The role of lipids in cell to hard surface adhesion is under investigation by modifying the surface lipids of the bacteria by selective enzyme action and by the employment of surfactants. Any interactions observed in the in vitro tests indicating therapeutic value will be tested in vivo in gnotobiotic rat models. Besides the cellular fatty acid composition of the oral Gram-positive rods (determined by gas liquid chromatography) as an aid in classification, the intact lipids are also under survey. Both of these results are being correlated with studies on the same group of organisms by this and other laboratories including: cell wall analyses, DNA base composition, metabolic reactions, antigenic relationships and other morphologic and biochemical characteristics, to establish the use of lipid "fingerprint" as a taxonomic variable in this difficult to classify group of microorganisms.